*{
    margin: 0px;
    padding: 0px;
}
body{
    height: 2000px;
}
ul{
    list-style: none;
}
/*设置总宽度*/
.nav{
    width: 1210px;
    height: 48px;
    background-color: #e8e7e3;
    margin-top: 100px;
    margin-left: auto;
    margin-right: auto;
    position: sticky;
    top:10px;
}

.nav li a{
    text-decoration: none;
    color: #777777;
    float: left;
    line-height: 48px;
    padding:0 39px;
    font-size: 20px;
}

.nav li a:hover{
    background-color: #3f3f3f;
    color: #fdfcf8;
}

.nav li:last-child a {
    padding-right: 48px;
    padding-left: 48px;
}
.top{
    display: block;
    position: fixed;
    bottom: 100px;
    right: 10px;
    width: 40px;
    height: 40px;
    background-color: #3f3f3f;
    font-size: 30px;
    color: #fdfcf8;
    text-align: center;
    text-decoration: none;
}
